Power supply apparatuses are essential for many electronic appliances such as personal computers, industrial computers, servers, communication products or network products. Usually, the user may simply plug a power supply apparatus into an AC wall outlet commonly found in most homes or offices so as to receive an AC voltage. The power supply apparatus will convert the AC voltage into a regulated DC output voltage for powering the electronic device and/or charging a battery built-in the electronic device.
Generally, power supply apparatuses are classified into two types, i.e. linear power supply apparatuses and switching power supply (SPS) apparatuses. A linear power supply apparatus principally comprises a transformer, diode rectifier and a capacitor filter. The linear power supply apparatus is advantageous due to its simplified circuitry and low fabricating cost. Since the linear power supply apparatus has bulky volume, the linear power supply apparatus is not applicable to a slim-type electronic device. In addition, the converting efficiency of the linear power supply apparatus is too low to comply with the power-saving requirements. In comparison with the linear power supply apparatus, the switching power supply apparatus has reduced volume but increased converting efficiency. That is, the switching power supply apparatus is applicable to the slim-type electronic device and may meet with the power-saving requirements.
As known, the electricity consumption amount of the electronic device is varied in different situations. For example, a power supply system may have multiple power supply apparatuses simultaneously providing electrical energy to the electronic device. The multiple power supply apparatuses could increase the power supply quantity. Even if the power supply quantity is sufficient to power the electronic device, one or more additional power supply apparatuses are served as backup power supply apparatuses in order to reduce the problems resulted from one or more damaged power supply apparatuses.
Since the speeds of initiating the conventional power supply apparatuses are very slow, if one of the power supply apparatuses has a breakdown, the backup power supply apparatuses need to be enabled to continuously provide electrical energy to the electronic device. If all power supply apparatuses are operated under light loads, the operating efficiency of each power supply apparatuses is insufficient. Moreover, if the electricity consumption amount of the electronic device is very low, the power supply amount is enough when some of the power supply apparatuses are enabled. Since all power supply apparatuses are enabled, the overall operating efficiency of the power supply system is reduced.
There is a need of providing a power supply system with multiple power supply apparatuses so as to obviate the drawbacks encountered from the prior art.